Circuit board with inspection terminals

ABSTRACT

Provided is a circuit board including inspection terminals, the circuit board including: a connection terminal, which is arranged on a front surface or in an inner layer of the circuit board, and is electrically connected to an object to be inspected; and three or more inspection terminals, which are electrically connected to the connection terminal, and are configured to measure a resistance value of the object be inspected, each of the three or more inspection terminals being arranged on a side surface of the circuit board.

BACKGROUND 1. Technical Field

The present application relates to a circuit board and a display device.

2. Description of the Related Art

A display device includes a display panel, a driver IC configured todrive the display panel, and a circuit board including a control circuitconfigured to control the driver IC. For example, the circuit board isconnected to the display panel via a flexible board. Further, electroniccomponents such as the driver IC are mounted by, for example, chip-onglass (COG) in which the electronic components are arranged on asubstrate of the display panel or chip-on film (COF) in which theelectronic components are arranged on the flexible board.

SUMMARY

In some cases, inspection terminals are mounted on the circuit board soas to measure a connection resistance between the boards or a connectionresistance between the driver IC and the board. The inspection terminalsare formed relatively larger so as to enable abutment of a measurementjig for resistance measurement. Therefore, the inspection terminals havelessened a region for arranging other electronic components or wirings.

The present application has been made in view of the above-mentionedproblem, and has an object to secure a larger region for arrangingcomponents or wirings in the circuit board including the inspectionterminals.

In order to solve the above-mentioned problem, according to oneembodiment of the present application, there is provided a circuitboard, including: a connection terminal, which is arranged on a frontsurface or in an inner layer of the circuit board, and is electricallyconnected to an object to be inspected; and three or more inspectionterminals, which are electrically connected to the connection terminal,and are configured to measure a resistance value of the object to beinspected, each of the three or more inspection terminals being arrangedon a side surface of the circuit board.

In the circuit board according to the one embodiment of the presentapplication, the connection terminal may be arranged on a first edgeside of the circuit board, and the each of the three or more inspectionterminals may be arranged on the side surface at an edge other than thefirst edge.

In the circuit board according to the one embodiment of the presentapplication, the each of the three or more inspection terminals may bearranged in a recessed shape in the side surface of the circuit board.

In the circuit board according to the one embodiment of the presentapplication, the each of the three or more inspection terminals may bearranged in a projecting shape in the side surface of the circuit board.

In the circuit board according to the one embodiment of the presentapplication, the each of the three or more inspection terminals may bearranged in a planar shape along the side surface of the circuit board.

In the circuit board according to the one embodiment of the presentapplication, the three or more inspection terminals may be arranged sideby side in one row along the side surface of the circuit board.

In the circuit board according to the one embodiment of the presentapplication, the three or more inspection terminals may have equaldistances between adjacent inspection terminals.

In the circuit board according to the one embodiment of the presentapplication, the three or more inspection terminals may have differentdistances between adjacent inspection terminals.

In the circuit board according to the one embodiment of the presentapplication, the connection terminal may include a first connectionterminal and a second connection terminal, the three or more inspectionterminals may include a first inspection terminal, a second inspectionterminal, and a third inspection terminal, the first connection terminalmay be electrically connected to the first inspection terminal via afirst connection wiring, the second connection terminal may beelectrically connected to the second inspection terminal and the thirdinspection terminal via a second connection wiring, and the secondconnection wiring may be formed so as to be extended from the secondconnection terminal, and then be branched to be connected to each of thesecond inspection terminal and the third inspection terminal.

In the circuit board according to the one embodiment of the presentapplication, the second connection wiring may be branched at a positioncloser to the second connection terminal than to the second inspectionterminal and the third inspection terminal.

In the circuit board according to the one embodiment of the presentapplication, the three or more inspection terminals may include seventerminals including a first inspection terminal, a second inspectionterminal, a third inspection terminal, a fourth inspection terminal, afifth inspection terminal, a sixth inspection terminal, and a seventhinspection terminal, the first inspection terminal, the secondinspection terminal, the third inspection terminal, and the fourthinspection terminal may be used for measuring a resistance value of afirst object to be inspected, the third inspection terminal, the fourthinspection terminal, the fifth inspection terminal, and the sixthinspection terminal may be used for measuring a resistance value of asecond object to be inspected, and the fourth inspection terminal, thefifth inspection terminal, the sixth inspection terminal, and theseventh inspection terminal may be used for measuring a resistance valueof a third object to be inspected.

In the circuit board according to the one embodiment of the presentapplication, parts of the each of the three or more inspection terminalsmay be arranged further on the front surface and a back surface of thecircuit board.

In the circuit board according to the one embodiment of the presentapplication, the side surface of the circuit board may have one of arecessed portion and a projecting portion formed therein so as toposition a measurement jig when the measurement jig is brought intoabutment against the three or more inspection terminals.

In the circuit board according to the one embodiment of the presentapplication, the circuit board may further include a connection wiringconfigured to electrically connect the connection terminal andcorresponding one of the three or more inspection terminals to eachother, and the connection wiring may be formed on a back surface or inthe inner layer of the circuit board.

In the circuit board according to the one embodiment of the presentapplication, the connection wiring may be electrically connected to theconnection terminal and corresponding one of the three or moreinspection terminals via a through hole formed through the circuitboard.

In the circuit board according to the one embodiment of the presentapplication, at least one of the three or more inspection terminals maybe electrically connected to a ground.

In the circuit board according to the one embodiment of the presentapplication, at least one of the three or more inspection terminals maybe electrically connected to a heat radiation pad configured to radiateheat of an IC included in the circuit board.

According to one embodiment of the present application, there isprovided a display device, including the above-mentioned circuit board.

In the display device according to one embodiment of the presentapplication, the display device may further include: a display panel; aframe, which is made of a metal, and is configured to support thedisplay panel from a back surface side thereof; and a protection tapeconfigured to cover the circuit board, the circuit board may be arrangedon a back surface side of the frame, the protection tape may beelectronically connected to at least one of the three or more inspectionterminals, and the protection tape may be electrically connected to theframe.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view for illustrating a schematic configurationof a display device according to an embodiment of the presentapplication.

FIG. 2 is a perspective view for illustrating an example of a controlcircuit board including a resistance measurement pad according to theembodiment.

FIG. 3 is a view for schematically illustrating objects to be inspectedaccording to the embodiment.

FIG. 4 is a view for illustrating a resistance measurement methodaccording to the embodiment.

FIG. 5 is a view for illustrating resistance value measurement at a COGconnection portion.

FIG. 6 is a view for illustrating resistance value measurement at a FOGconnection portion.

FIG. 7 is a view for illustrating resistance value measurement at a FOBconnection portion.

FIG. 8 is a view for illustrating the configuration of wiring of thecontrol circuit board.

FIG. 9 is a perspective view for illustrating an example of the controlcircuit board including the resistance measurement pad according to theembodiment.

FIG. 10 is perspective view for illustrating an example of the controlcircuit board including the resistance measurement pad according to theembodiment.

FIG. 11 is a perspective view for illustrating an example of the controlcircuit board including the resistance measurement pad according to theembodiment.

FIG. 12 is a perspective view for illustrating an example of the controlcircuit board including the resistance measurement pad according to theembodiment.

FIG. 13 is a view for illustrating an example of a probe pin to bebrought into abutment against the resistance measurement pad.

FIG. 14 is a perspective view for illustrating an example of the controlcircuit board including the resistance measurement pad according to theembodiment.

FIG. 15 is a view for illustrating an example of connection wiringformed to the control circuit board.

FIG. 16 is a view for schematically illustrating the control circuitboard in which a part of the resistance measurement pad is connected tothe ground.

FIG. 17 is a sectional view of a display device to which the controlcircuit board illustrated in FIG. 16 is applied.

FIG. 18 is a view for schematically illustrating the control circuitboard in which a part of the resistance measurement pad is connected toa heat radiation pad.

FIG. 19 is a view for schematically illustrating an inner layer of thecontrol circuit board illustrated in FIG. 18.

FIG. 20 is a view for schematically illustrating the control circuitboard in which the ground and the heat radiation pad are connected tothe resistance measurement pad.

DETAILED DESCRIPTION

Now, an embodiment of the present application is described withreference to the drawings. In the embodiment of the present application,as an example of a circuit board, a control circuit board included in adisplay device is exemplified, but the present application is notlimited to this example, and the circuit board may be a circuit boardincluded in other apparatus. Note that, in the drawings, the same orequivalent elements are denoted by the same reference symbols, andredundant description thereof is omitted.

FIG. 1 is a perspective view for illustrating a schematic configurationof a display device 1 according to this embodiment. As illustrated inFIG. 1, the display device 1 includes a display panel 10 configured todisplay an image, a driver IC 20 configured to drive the display panel10, a flexible printed board (FPC) 40, a control circuit board 50 havingmounted thereon a control circuit configured to control the driver IC20, and a backlight unit (not shown) configured to irradiate the displaypanel 10 with light from the back surface side.

The display panel 10 includes the driver IC 20 serving as a drivecircuit used for displaying an image. The display device 1 according tothis embodiment employs a COG system in which the driver IC 20 isdirectly mounted on a glass substrate of the display panel 10. Notethat, the display panel 10 may employ a COF system in which the driverIC 20 is mounted on the FPC 40.

The control circuit board 50 is electrically connected to the displaypanel 10 via the FPC 40. The control circuit board 50 has, for example,a timing controller mounted thereon, which is configured to control theoperation of the driver IC 20. The control circuit board 50 may be arigid board, or a rigid flexible board integrally formed with the FPC40.

Further, the control circuit board 50 includes inspection terminals. Theinspection terminals are terminals used for performing variousinspections in the display device 1. In the following, the inspectionterminals in this embodiment are described as a resistance measurementpad 60 including inspection terminals configured to measure a resistanceof an object to be inspected.

FIG. 2 is a perspective view for illustrating an example of the controlcircuit board 50 including the resistance measurement pad 60 accordingto this embodiment. As illustrated in FIG. 2, in the control circuitboard 50 according to this embodiment, a connection terminal 70electrically connected to an object to be inspected is arranged on afront surface of the control circuit board 50. Further, on a sidesurface of the control circuit board 50, the resistance measurement pad60 being electrically connected to the connection terminal 70 andincluding three or more inspection terminals 61 (in FIG. 2, seveninspection terminals 61) configured to measure the resistance value ofthe object to be inspected is arranged. A measurement jig such as probepins Pr is brought into abutment against the resistance measurement pad60. In FIG. 2, for the sake of convenience, the illustration ofelectronic components and wiring patterns other than the connectionterminal 70 and the resistance measurement pad 60 is omitted. In thisembodiment, the FPC 40 (not shown) is electrically connected to theconnection terminal 70, and the control circuit board 50 and the displaypanel 10 (not shown) are electrically connected to each other via theFPC 40. Therefore, the connection terminal 70 is arranged on the frontsurface of the control circuit board 50 on a first edge 51 side, and theresistance measurement pad 60 is arranged on the side surface on asecond edge 52 side opposed to the first edge 51 at which the connectionterminal 70 is arranged. Note that, the resistance measurement pad 60may be arranged on a side surface on a third edge 53 side connecting thefirst edge 51 and the second edge 52 or on a fourth edge 54 sideconnecting the first edge 51 and the second edge 52. In other words, theresistance measurement pad 60 may be arranged on a side surface at anedge different from the first edge 51 at which the connection terminal70 is arranged. By arranging the resistance measurement pad 60 on a sidesurface around which the FPC 40 and the display panel 10 are notarranged as described above, the probe pins Pr can be easily broughtinto abutment against the resistance measurement pad 60. Further, theresistance measurement pad 60 may be arranged on the side surface on thefirst edge 51 side on which the connection terminal 70 is arranged. Notethat, the connection terminal 70 is not limited to the example in whichthe connection terminal 70 is arranged along the edge of the controlcircuit 50, and may be arranged at a center portion of the controlcircuit board 50. In this case, the resistance measurement pad 60 may bearranged on any side surface of the control circuit board 50.

FIG. 3 is a view for schematically illustrating the objects to beinspected according to this embodiment. As illustrated in FIG. 3, afirst object to be inspected in this embodiment is a connection portionbetween the glass substrate of the display panel 10 and the driver IC 20(hereinafter referred to as “COG connection portion 200”), a secondobject to be inspected is a connection portion between the glasssubstrate of the display panel 10 and the FPC 40 (hereinafter referredto as “FOG connection portion 300”), and a third object to be inspectedis a connection portion between the control circuit board 50 (in thisembodiment, the connection terminal 70 of the control circuit board 50)and the FPC 40 (hereinafter referred to as “FOB connection portion400”). The control circuit board 50 and the FPC 40, the FPC 40 and theglass substrate of the display panel 10, and the glass substrate of thedisplay panel 10 and the driver IC 20 are each pressure bonded to eachother with use of an anisotropic conductive film to secure electricalconnection. A connection terminal group of each pressure-bonded portioncorresponds to the object to be inspected according to this embodiment.In FIG. 3, the COG connection portion 200 includes two COG connectionterminals 201, the FOG connection portion 300 includes five FOGconnection terminals 301, and the FOB connection portion 400 includessix connection terminals 70. Further, in order to measure the resistancevalues of three positions, specifically, the COG connection portion 200,the FOG connection portion 300, and the FOB connection portion 400, theresistance measurement pad 60 includes seven inspection terminals 61(first inspection terminal 61 a to seventh inspection terminal 61 g).The seven inspection terminals 61 of the resistance measurement pad 60are arranged side by side in one row on the side surface of the controlcircuit board 50. Each COG connection terminal 201 of the COG connectionportion 200 and each FOG connection terminal 301 of the FOG connectionportion 300 are electrically connected to each other via a wiring. EachFOG connection terminal 301 of the FOG connection portion 300 and eachconnection terminal 70 of the FOB connection portion 400 areelectrically connected to each other via a wiring. Each connectionterminal 70 and each inspection terminal 61 are electrically connectedto each other via a wiring. In this case, the resistance values of theCOG connection portion 200, the FOG connection portion 300, and the FOBconnection portion 400 are measured to inspect the connectionreliability at each connection portion. Note that, the configuration ofthe object to be inspected and the wiring patterns illustrated in FIG. 3are suitable for resistance measurement using a four-terminal method tobe described later, but the configuration of the object to be inspectedand the wiring patterns are not limited to this example.

FIG. 4 is a view for illustrating a resistance measurement methodaccording to this embodiment. In this embodiment, a measurement device100 performs resistance measurement by a so-called four-terminal methodusing four probe pins Pr (Pr1, Pr2, Pr3, and Pr4). The four-terminalmethod is a measurement method used for low-resistance measurement, andis effective for an object to be inspected having a low contactresistance and being susceptible to the wiring resistance. Theresistance value of the COG connection portion 200 is about several tensof Ω, the resistance value of the FOG connection portion 300 is aboutseveral Ω, and the resistance value of the FOB connection portion 400 isabout several tens of mΩ. Therefore, the contact resistance of eachconnection portion is low, and hence the measurement by thefour-terminal method is effective in this embodiment. The measurementdevice 100 includes a constant current source, an ammeter, and avoltmeter. The probe pin Pr1 and the probe pin Pr4 are connected to theconstant current source to supply a constant current between measurementpoints of the object to be inspected. The probe pin Pr2 and the probepin Pr3 are connected to the voltmeter to detect a voltage value betweenmeasurement points. The measurement device 100 is configured to cause apredetermined current to flow from the constant current source to theobject to be inspected, and to cause the ammeter to detect the currentflowing through the object to be inspected and cause the voltmeter todetect the voltage generated between the measurement points of theobject to be inspected. Further, the measurement device 100 isconfigured to calculate the resistance value of the object to beinspected by dividing the voltage value detected by the voltmeter by thecurrent value detected by the ammeter. In this case, the currentsupplied from the constant current source hardly flows through a pathpassing through the probe pin Pr2, the voltmeter, and the probe pin Pr3during voltage detection by the voltmeter. Therefore, without beingaffected by the voltage drop caused by the wiring resistance in a regionfrom the object to be inspected to the resistance measurement pad 60,the resistance value of the object to be inspected can be measured athigh accuracy.

Next, a method of measuring the resistance value of each connectionportion is described with reference to FIG. 5 to FIG. 7.

FIG. 5 is a view for illustrating resistance value measurement at theCOG connection portion 200. As illustrated in FIG. 5, the firstinspection terminal 61 a, the second inspection terminal 61 b, the thirdinspection terminal 61 c, and the fourth inspection terminal 61 d areused for measuring the resistance value of the COG connection portion200. The probe pin Pr1 to the probe pin Pr4 are brought into abutmentagainst the first inspection terminal 61 a to the fourth inspectionterminal 61 d, respectively. Thus, a current flows along a pathrepresented by the thick line to measure the resistance value of the COGconnection portion 200. In FIG. 5, the resistance values of the two COGconnection terminals 201 are measured.

FIG. 6 is a view for illustrating resistance value measurement at theFOG connection portion 300. As illustrated in FIG. 6, the thirdinspection terminal 61 c to the sixth inspection terminal 61 f are usedfor measuring the resistance value of the FOG connection portion 300.The probe pin Pr1 to the probe pin Pr4 are brought into abutment againstthe third inspection terminal 61 c to the sixth inspection terminal 61f, respectively. Thus, a current flows along a path represented by thethick line to measure the resistance value of the FOG connection portion300. In FIG. 6, the resistance value of the rightmost FOG connectionterminal 301 is measured.

FIG. 7 is a view for illustrating resistance value measurement at theFOB connection portion 400. As illustrated in FIG. 7, the fourthinspection terminal 61 d to the seventh inspection terminal 61 g areused for measuring the resistance value of the FOB connection portion400. The probe pin Pr1 to the probe pin Pr4 are brought into abutmentagainst the fourth inspection terminal 61 d to the seventh inspectionterminal 61 g, respectively. Thus, a current flows along a pathrepresented by the thick line to measure the resistance value of the FOBconnection portion 400. In FIG. 7, the resistance value of the rightmostCOG connection terminal 70 is measured.

In FIG. 5 to FIG. 7, the current path includes branching points (X2 andX3) at which the path is branched to the wiring passing through theprobe pin Pr2, the voltmeter, and the probe pin Pr3. In this case, theresistance measurement by the four-terminal method can measure theresistance value of the object to be inspected at high accuracy withoutbeing affected by the voltage drop caused by the wiring resistance, butthe measurement is affected by the voltage drop caused by the wiringresistances in a path between the branching point X2 and the object tobe inspected and in a path between the object to be inspected and thebranching point X3. For example, the measurement value includes wiringresistances in a path (path R2) from the branching point X2 to theconnection terminal 70 serving as the object to be inspected and in apath (path R3) from the connection terminal 70 serving as the object tobe inspected to the branching point X3, which are illustrated in FIG. 7.In view of this, in order to measure the resistance value of the objectto be inspected at high accuracy while reducing the influence of thewiring resistances of the path R2 and the path R3, it is preferred thatthe wiring of the path R2 and the path R3 be short and thick so as toreduce the wiring resistances of the path R2 and the path R3.

Specifically, description is given of the configuration of the wiringfor reducing the wiring resistance in the path between the branchingpoint and the object to be inspected when the resistance of the FOBconnection portion 400 is measured. FIG. 8 is a view for illustratingthe configuration of the wiring of the control circuit board 50. Asillustrated in FIG. 8, the control circuit board 50 has formed thereonthe resistance measurement pad 60 including the seven inspectionterminals 61 (first inspection terminal 61 a to seventh inspectionterminal 61 g) and the FOB connection portion 400 including the sixconnection terminals 70 (70 a to 70 f). Further, connection wirings 80(80 a to 80 e) configured to electrically connect between the connectionterminals 70 a to 70 e and the first inspection terminal 61 a to thefifth inspection terminal 61 e, respectively, are formed. The connectionterminal 70 f is electrically connected to the sixth inspection terminal61 f and the seventh connection terminal 61 g via a connection wiring 80f. Further, the connection wiring 80 f is formed so as to be extendedfrom the connection terminal 70 f, and then be branched to be connectedto each of the sixth inspection terminal 61 f and the seventh inspectionterminal 61 g. In this case, it is assumed that, when the resistance ofthe FOB connection portion 400 is measured, the resistance value of theconnection terminal 70 f is measured. As described above, by forming theconnection wiring 80 f electrically connected to the connection terminal70 f serving as the object to be inspected so as to be branched, ascompared to the case where the connection wiring 80 f is formed so asnot to be branched, the path between the object to be inspected and thebranching point can be shortened. As a result, the wiring resistancebetween the object to be inspected and the branching point can bereduced.

Further, it is preferred that the position at which the connectionwiring 80 f is branched be closer to the connection terminal 70 f thanto the sixth inspection terminal 61 f and the seventh inspectionterminal 61 g. With this, the path between the object to be inspectedand the branching point can be further shortened. The wiring resistancebetween the object to be inspected and the branching point can bereduced.

Note that, each connection terminal 70 and each inspection terminal 61may be connected on a one-to-one basis without branching the connectionwiring 80 f. In this case, a seventh connection terminal 70 g may beformed so that the seventh connection terminal 70 g and the seventhinspection terminal 61 g are electrically connected to each other.

As described above, by arranging the seven inspection terminals 61 ofthe resistance measurement pad 60 side by side in one row, and sharing apart of the inspection terminals 61 with the plurality of objects to beinspected, the number of terminals of the resistance measurement pad 60can be reduced. Note that, the number of terminals of the resistancemeasurement pad 60 may be 8 or more.

Further, the three or more inspection terminals 61 forming theresistance measurement pad 60 may have equal distances between adjacentinspection terminals 61. By arranging the three or more inspectionterminals 61 at equal intervals side by side, the plurality of probepins Pr can be easily and simultaneously brought into abutment againstthe resistance measurement pad 60. Further, when the measurement isperformed while sequentially shifting the probe pins Pr, such as whenthe measurement of the COG connection portion 200, the measurement ofthe FOG connection portion 300, and the measurement of the FOBconnection portion 400 are sequentially performed, the probe pins Pr maybe easily brought into abutment against the resistance measurement pad60. Note that, the distance between the adjacent inspection terminals 61may vary in the three or more inspection terminals 61 forming theresistance measurement pad 60.

Further, the measurement device 100 may be configured to measure theresistance value of the object to be inspected by a three-terminalmethod. The three-terminal method is a measurement method to be used inlow-resistance or high-resistance measurement. In the measurement methodto be used for the purpose of low-resistance measurement, the resistancevalue of the object to be inspected can be measured at high accuracywithout being affected by the voltage drop caused by the wiringresistance in the region from the object to be inspected to theresistance measurement pad 60, though not to the extent of thefour-terminal method. In the measurement method to be used for thepurpose of high-resistance measurement, whether or not the object to beinspected is short-circuited and a desired insulating resistance issecured can be inspected. Further, the measurement device 100 may beconfigured to measure the impedance of the object to be inspected by afive-terminal method. In the five-terminal method, the impedance of theobject to be inspected can be measured at high accuracy without beingaffected by the capacitance between the object to be inspected and thesurrounding metal.

Note that, the resistance measurement pad 60 may include terminals formeasurement by the three-terminal method and terminals for measurementby the four-terminal method in a mixed manner. For example, among theCOG connection portion 200, the FOG connection portion 300, and the FOBconnection portion 400, the COG connection portion 200 has a relativelyhigher resistance value, and hence the resistance value thereof may bemeasured by the three-terminal method. By measuring the resistance valueof a part of the objects to be inspected by the three-terminal method,the number of terminals of the resistance measurement pad 60 can bereduced. Further, when there are provided an object to be inspectedwhose connection reliability is inspected and an object to be inspectedwhose securement of an insulating resistance is inspected, theresistance measurement pad 60 may include terminals for measurement bythe three-terminal method and terminals for measurement by thefour-terminal method in a mixed manner. Further, the resistancemeasurement pad 60 may include terminals for measurement by thefive-terminal method in a mixed manner.

Further, the object to be measured may be one or two of the COGconnection portion 200, the FOG connection portion 300, and the FOBconnection portion 400 described above. When one object is to bemeasured, the measurement device 100 can measure the resistance value ofthe object to be inspected as long as the resistance measurement pad 60includes at least three inspection terminals 61. Further, the object tobe measured is not limited to the COG connection portion 200, the FOGconnection portion 300, and the FOB connection portion 400 describedabove, and the connection portion between another electronic componentand the board may be the object to be measured.

Further, each inspection terminal 61 of the resistance measurement pad60 is formed to be relatively larger to enable abutment of the probe pinPr. Therefore, when the resistance measurement pad 60 is arranged on thefront surface of the control circuit board 50, the region for arrangingother electronic components or wirings is lessened. In this embodiment,by arranging the resistance measurement pad 60 on the side surface ofthe control circuit board 50, a large region is secured for arrangingelectronic components or wirings on the front surface of the controlcircuit board 50. Further, in this embodiment, the measurement device100 is configured to measure the resistance value of the object to beinspected by the three-terminal method or the four-terminal method, andhence the measurement is not affected by the voltage drop caused by thewiring resistance in the region from the object to be inspected to theresistance measurement pad 60. Therefore, the wiring path of theconnection wiring 80 for electrical connection between each connectionportion and each inspection terminal 61 may be long, and thus theresistance value can be measured at high accuracy even when theresistance measurement pad 60 is arranged on the side surface of thecontrol circuit board 50.

Next, the specific shape of the resistance measurement pad 60 accordingto this embodiment is described. FIG. 9 to FIG. 14 are perspective viewsfor illustrating examples of the control circuit board 50 including theresistance measurement pad 60 according to this embodiment.

In the control circuit board 50 illustrated in FIG. 9, each inspectionterminal 61 of the resistance measurement pad 60 is formed. into arecessed shape in the side surface of the control circuit board 50. Byforming each inspection terminal 61 of the resistance measurement pad 60into a recessed shape, the probe pins Pr can be easily positioned.Further, the probe pins Pr are less liable to be shifted in the lateraldirection when being brought into abutment against the inspectionterminals 61. Therefore, the probe pins Pr can be easily brought intoabutment against the inspection terminals 61.

In the control circuit board illustrated in FIG. 10, each inspectionterminal 61 of the resistance measurement pad 60 is formed into aprojecting shape in the side surface of the control circuit board 50. Byforming each inspection terminal 61 of the resistance measurement pad 60into a projecting shape, a recess between two adjacent terminals can beused for positioning the probe pins Pr. For example, when a measurementjig unit 110 capable of arranging the four probe pins Pr atpredetermined intervals (for example, at intervals of two adjacentinspection terminals 61) is used, a protrusion 111 is provided to themeasurement jig unit 110 between two adjacent probe pins Pr so as tocorrespond to the recess between the two inspection terminals 61. Then,by fitting the protrusion 111 to the recess between the two inspectionterminals 61, the probe pins Pr can be positioned. Further, by fittingthe protrusion 111 to the recess between the two inspection terminals61, the probe pins Pr are less liable to be shifted in the lateraldirection when being brought into abutment against the inspectionterminals 61. Therefore, the probe pins Pr can be easily brought intoabutment against the inspection terminals 61.

In the control circuit board 50 illustrated in FIG. 11, each inspectionterminal 61 of the resistance measurement pad 60 is formed into a planarshape along the side surface of the control circuit board 50. Further,in the control circuit board 50 illustrated in FIG. 12, each inspectionterminal 61 of the resistance measurement pad 60 is formed into a planarshape along the side surface of the control circuit board 50, andfurther parts of each inspection terminal 61 are arranged on the frontsurface and the back surface of the control circuit board 50. Forexample, each inspection terminal 61 is formed so as to be extended fromthe side surface of the control circuit board 50 to the front surfaceand the back surface. Note that, a part of each inspection terminal 61may be arranged on the front surface or the back surface of the controlcircuit board 50. FIG. 13 is a view for illustrating an example of theprobe pin Pr to be brought into abutment against the resistancemeasurement pad 60 illustrated in FIG. 12. FIG. 13 is a view forillustrating the control circuit board 50 as viewed from the sidesurface side. As illustrated in FIG. 13, the probe pin Pr is bent so asto extend along the front surface of the resistance measurement pad 60,and a leading end of the probe pin Pr is formed so as to be brought intoabutment against a part of the inspection terminal 61 arranged on thefront surface of the control circuit board 50. With this, the probe pinPr can be easily held under a state in which the leading end of theprobe pin Pr is brought into abutment against the inspection terminal61. Abutment of the probe pin Pr against the planar terminal illustratedin FIG. 11 is difficult in positioning because the leading end of theprobe pin Pr is liable to be misaligned. However, by using theinspection terminal 61 and the probe pin Pr as illustrated in FIG. 13,the probe pin Pr can be easily brought into abutment against theinspection terminal 61.

In the control circuit board 50 illustrated in FIG. 14, recessed portion150 for positioning are formed in the side surface on which theresistance measurement pad 60 is arranged. Further, in the measurementjig unit 110, a projecting portion 152 is formed so as to correspond tothe recessed portions 150 for positioning formed in the control circuitboard 50. The recessed portions 150 and the projecting portion 151 areformed at positions based on the combination of the inspection terminals61 against which the probe pins Pr are brought into abutment. Further,the recessed portions 150 may be formed as many as the number of theobjects to be measured. By fitting projecting portion 152 of themeasurement jig unit 110 to the recessed portion 150 formed in thecontrol circuit board 50, the probe pins Pr are brought into abutmentagainst the predetermined inspection terminals 61. Abutment of the probepins Pr to the planar inspection terminals 61 illustrated in FIG. 11 isdifficult in positioning because the leading ends of the probe pins Prare liable to be misaligned. However, by using the control circuit board50 and the measurement jig unit 110 as illustrated in FIG. 14, the probepins Pr can be easily brought into abutment against the inspectionterminals 61. Note that, the projecting portion for positioning may beformed on the control circuit board 50, and the recessed portionscorresponding to the projecting portion for positioning may be formed inthe measurement jig unit 110.

Further, the connection wiring 80 configured to electrically connecteach connection portion and each inspection terminal 61 to each othermay be formed on the front surface of the control circuit board 50, orat least a part of the connection wiring 80 may be formed on the backsurface or in the inner layer of the control circuit board 50. FIG. 15is a view for illustrating an example of the connection wiring 80 formedto the control circuit board 50. In FIG. 15, for the sake ofconvenience, only the connection wiring 80 f connected to the seventhinspection terminal 61 g is illustrated, but the same applies to theconnection wirings 80 a to 80 f connected to the first inspectionterminal 61 a to the sixth inspection terminal 61 f, respectively.

As illustrated in FIG. 15, the connection wiring 80 f includes a firstconnection wiring 81 f, a second connection wiring 82 f, and a thirdconnection wiring 83 f. The first connection wiring 81 f is formed onthe front surface of the control circuit board 50 to electricallyconnect between the connection terminal 70 and a first through hole 90.In plan view, the first through hole 90 is formed at a positionseparated away from the connection terminal 70. The second connectionwiring 82 f is formed in the inner layer of the control circuit board 50to electrically connect between the first through hole 90 and a secondthrough hole 91. The second through hole 91 is formed below theconnection terminal 70. The third connection wiring 83 f is formed onthe back surface of the control circuit board 50 to electrically connectbetween the second through hole 91 and the seventh inspection terminal61 g. The first connection wiring 81 f and the second connection wiring82 f are electrically connected to each other via the first through hole90. Further the second connection wiring 82 f and the third connectionwiring 83 f are electrically connected to each other via the secondthrough hole 91.

As described above, by forming at least a part of the connection wiring80 f in the inner layer or on the back surface of the control circuitboard 50, a large region can be secured for arranging electroniccomponents or wirings on the front surface of the control circuit board50. In particular, in the resistance measurement by the four-terminalmethod, the resistance value of the object to be inspected can bemeasured without being affected by the voltage drop caused by the wiringresistance in the region from the object to be inspected to theresistance measurement pad 60. Therefore, the wiring path of theconnection wiring 80 f may be long. Therefore, the connection wiring 80f can be routed in a region of the control circuit board 50 in whichelectronic components or major wirings are not formed. In FIG. 15, thesecond through hole 91 is formed below the connection terminal 70, andthe third connection wiring 83 f is formed on the back surface of thecontrol circuit beard 50 where the wiring is not formed.

Note that, the wiring pattern of the connection wiring 80 f is notlimited to the example illustrated in FIG. 15. For example, the thirdconnection wiring 83 f may be formed in a layer different from the layerin which the second connection wiring 82 f is formed in the inner layerof the control circuit board 50. Further, without forming the secondthrough hole 91 and the second connection wiring 82 f, the firstconnection wiring 81 f and the third connection wiring 83 f may beelectrically connected to each other via the first through hole 90. Asdescribed above, the connection wiring 80 f can be freely routed to aregion that does not hinder the wiring pattern of the control circuitboard 50 depending on the wiring pattern of the control circuit board50.

Further, in the control circuit board 50 of this embodiment, a part ofthe resistance measurement pad 60 may be connected to the ground. FIG.16 is a view for schematically illustrating the control circuit board 50in which a part of the resistance measurement pad 60 is connected to theground. FIG. 17 is a sectional view of the display device 1 to which thecontrol circuit board 50 illustrated in FIG. 16 is applied. In FIG. 17,the first inspection terminal 61 a and the seventh inspection terminal61 g are connected to the signal ground of the control circuit board 50.The signal ground is formed in the inner layer or on the back surface ofthe control circuit board 50, for example. Note that, when a part of theresistance measurement pad 60 is connected to the signal ground of thecontrol circuit board 50, occurrence of short-circuit between theinspection terminals 61, by which the inspection by the four-terminalmethod may be affected, is prevented. Further, it is preferred toshorten and thicken the path extending from the inspection terminal 61to the ground as much as possible so as to reduce the wiring resistance.

As illustrated in FIG. 17, a metallic frame 120 configured to supportthe display panel 10 is arranged on the back surface side of the displaypanel 10. The control circuit board 50 is arranged on the back surfaceside of the frame 120. Further, the control circuit board 50 is fixed tothe frame 120 by an insulating tape 130. Further, a protection covertape 110 is arranged so as to cover the control circuit board 50 and theFPC 40. The protection cover tape 110 has a layer structure in which aconductive member such as a copper foil is sandwiched between insulatingfilms from both sides. Then, in a region in which the protection covertape 110 and the control circuit board 50 (in this case, the resistancemeasurement pad 60 arranged on the side surface of the control circuitboard 50) are in contact with each other, the protection cover tape 110is bonded to a part of the resistance measurement pad 60 so as to beelectrically connected thereto. Further, in a region in which theprotection cover tape 110 and the lower frame 120 are in contact witheach other, the protection cover tape 110 is bonded to the lower frame120 so as to be electrically connected thereto. In this case, theprotection cover tape 110 is bonded to the first inspection terminal 61a and the seventh inspection terminal 61 g illustrated in FIG. 16 so asto be electrically connected thereto. As described above, the signalground of the control circuit board 50 is connected to the frame groundvia the resistance measurement pad 60 (in this case, the firstinspection terminal 61 a and the seventh inspection terminal 61 g),thereby being capable of reducing the discharge of the electromagneticwaves from the circuit components mounted on the control circuit board50 and reducing the influence of the electromagnetic waves applied fromthe periphery. In general, the resistance measurement pad 60 serving asthe inspection terminals is unnecessary after the inspection is endedand the display device 1 is assembled, but according to thisconfiguration, the resistance measurement pad 60 can be used forblocking electromagnetic waves of the control circuit board 50 evenafter the display device 1 is assembled. Further, it is unnecessary toseparately form a ground opening portion in the front surface of thecontrol circuit board 50 for electrical connection to the protectioncover tape 110, and a large region can be secured for arrangingelectronic components or wirings in the control circuit board 50.

Further, in the control circuit board 50 of this embodiment, a part ofthe resistance measurement pad 60 may be connected to a heat radiationterminal. The heat radiation terminal is assumed to be, for example, aheat radiation pad 250 (see FIG. 18) formed for heat radiation of an ICmounted on the control circuit board 50. FIG. 18 is a view forschematically illustrating the control circuit board 50 in which a partof the resistance measurement pad 60 is connected to the heat radiationpad 250. In FIG. 18, the first inspection terminal 61 a and the heatradiation pad 250 are electrically connected to each other, therebybeing capable of promoting the heat radiation of the IC by the firstinspection terminal 61 a. In general, the resistance measurement pad 60serving as the inspection terminals is unnecessary after the inspectionis ended and the display device 1 is used, but according to thisconfiguration, the resistance measurement pad 60 can be used forpromoting the heat radiation of the IC mounted on the control circuitboard 50 even during use of the display device 1.

In this case, it is preferred to shorten and thicken the wiring pathextending from the inspection terminal 61 to the heat radiation pad 250or the wiring path extending from the inspection terminal 61 to thesignal ground as much as possible so as to reduce the wiring resistance.By reducing the wiring resistance in the region from the inspectionterminal 61 to the heat radiation pad 250, the heat radiation effect canbe enhanced, and by reducing the wiring resistance in the region fromthe inspection terminal 61 to the signal ground, the electromagneticwave blocking effect can be enhanced. For example, by connecting theheat radiation pad 250 to the inspection terminal 61 positioned close tothe heat radiation pad 250, the wiring resistance can be reduced.Further, by forming a plurality of wiring paths extending from theinspection terminal 61 to the heat radiation pad 250, and causing thewiring paths to pass through different layers of the control circuitboard 50, the wiring resistance can be reduced. Similarly, by forming aplurality of wiring paths extending from the inspection terminal 61 tothe signal ground, and causing the wiring paths to pass throughdifferent layers of the control circuit board 50, the wiring resistancecan be reduced.

The configuration of forming a plurality of wiring paths extending fromthe inspection terminal 61 to the heat radiation pad 250 is describedwith reference to FIG. 19. FIG. 19 is a view for schematicallyillustrating the inner layer of the control circuit board 50 illustratedin FIG. 18. In FIG. 19, for the sake of convenience, only the firstinspection terminal 61 a of the resistance measurement pad 60 isillustrated. As illustrated in FIG. 19, two wirings connected to thefirst inspection terminal 61 a (heat radiation pad connection wiring 151and heat radiation pad connection wiring 152) are formed, and the heatradiation pad connection wiring 151 and the heat radiation padconnection wiring 152 are formed in layers different from each other.Further, the first inspection terminal 61 a and the heat radiation pad250 are electrically connected to each other via the heat radiation padconnection wiring 151 and the heat radiation pad connection wiring 152.Further, the beat radiation pad connection wiring 151 and the heatradiation pad connection wiring 152 are electrically connected to theheat radiation pad 250 via through holes 158. As described above, byelectrically connecting the first inspection terminal 61 a and the heatradiation pad 250 to each other via a plurality of layers of the controlcircuit board 50, the wiring resistance between the first inspectionterminal 61 a and the heat radiation pad 250 can be reduced to enhancethe heat radiation effect. Further, the heat radiation pad connectionwiring 151 and the heat radiation pad connection wiring 152 areelectrically connected to each other via plurality of through holes 159,thereby being capable of further reducing the wiring resistance.Further, the heat radiation pad 250 has the ground potential in manycases, and hence the effect of blocking electromagnetic waves of thecontrol circuit board 50 is also obtained together with the enhancementof the heat radiation effect.

Further, in FIG. 19, similarly to the connection wiring 80 f illustratedin FIG. 15, the connection wiring 80 a includes a first connectionwiring 81 a formed on the front surface of the control circuit board 50,a second connection wiring 82 a formed in the inner layer of the controlcircuit board 50, and a third connection wiring 83 a formed on the backsurface of the control circuit board 50. In this case, the heatradiation pad connection wiring 151 and the second connection wiring 82a or the third connection wiring 83 a may be formed in the same layer,or may be formed in layers different from each other. Further, the heatradiation pad connection wiring 152 and the second connection wiring 82a or the third connection wiring 83 a may be formed in the same layer,or may be formed in layers different from each other.

Note that, in the configuration of forming a plurality of wiring pathsextending from the inspection terminal 61 to the signal ground when theheat radiation pad 250 and the heat radiation pad connection wiring arereplaced with the ground and the ground connection wiring, respectively,in the above description, there is obtained a configuration similar tothe configuration illustrated in FIG. 19.

Further, the configuration illustrated in FIG. 16 and the configurationillustrated in FIG. 18 may be combined with each other for use. FIG. 20is a view for schematically illustrating the control circuit board 50 inwhich the ground and the heat radiation pad are connected to theresistance measurement pad 60. In FIG. 20, the first inspection terminal61 a is electrically connected to the signal ground and the heatradiation pad 250. Other configurations are similar to those describedwith reference to FIG. 16 to FIG. 19, and hence description thereof isomitted. As described above, by electrically connecting the firstinspection terminal 61 a to the signal ground and the heat radiation pad250, the configuration becomes more effective for the blocking of theelectromagnetic waves of the control circuit board 50 and the heatradiation of the IC mounted on the control circuit board 50.

While there have been described what are at present considered to becertain embodiments of the application, it will be understood thatvarious modifications may be made thereto, and it is intended that theappended claims cover all such modifications as fall within the truespirit and scope of the invention.

What is claimed is:
 1. A circuit board, comprising: a connectionterminal, which is arranged on a front surface or in an inner layer ofthe circuit board, and is electrically connected to an object to beinspected; three or more inspection terminals, which are electricallyconnected to the connection terminal, and are configured to measure aresistance value of the object to be inspected, each of the three ormore inspection terminals being arranged on a side surface of thecircuit board; and a plurality of recessed portions formed on the sidesurface of the circuit board, a distance between two adjacent recessedportions from the plurality of recessed portions being the same as adistance between two adjacent inspection terminals from the three ormore inspection terminals, wherein the three or more inspectionterminals are arranged in a planar shape along the side surface of thecircuit board.
 2. The circuit board according to claim 1, wherein theconnection terminal is arranged on a first edge side of the circuitboard, and wherein the three or more inspection terminals are arrangedon the side surface at an edge other than the first edge.
 3. The circuitboard according to claim 1, wherein the three or more inspectionterminals are arranged side by side in one row along the side surface ofthe circuit board.
 4. The circuit board according to claim 3, whereinthe three or more inspection terminals have equal distances betweenadjacent inspection terminals.
 5. The circuit board according to claim3, wherein the three or more inspection terminals have differentdistances between adjacent inspection terminals.
 6. The circuit boardaccording to claim 1, wherein the connection terminal comprises a firstconnection terminal and a second connection terminal, wherein the threeor more inspection terminals comprise a first inspection terminal, asecond inspection terminal, and a third inspection terminal, wherein thefirst connection terminal is electrically connected to the firstinspection terminal via a first connection wiring, wherein the secondconnection terminal is electrically connected to the second inspectionterminal and the third inspection terminal via a second connectionwiring, and wherein the second connection wiring is formed so as to beextended from the second connection terminal, and then be branched to beconnected to each of the second inspection terminal and the thirdinspection terminal.
 7. The circuit board according to claim 6, whereinthe second connection wiring is branched at a position closer to thesecond connection terminal than to the second inspection terminal andthe third inspection terminal.
 8. The circuit board according to claim1, wherein be three or more inspection terminals comprise seventerminals comprising a first inspection terminal, a second inspectionterminal, a third inspection terminal, a fourth inspection terminal, afifth inspection terminal, a sixth inspection terminal, and a seventhinspection terminal, wherein the first inspection terminal, the secondinspection terminal, the third inspection terminal, and the fourthinspection terminal are used for measuring a resistance value of a firstobject to be inspected, wherein the third inspection terminal, thefourth inspection terminal, the fifth inspection terminal, and the sixthinspection terminal are used for measuring a resistance value of asecond object to be inspected, and wherein the fourth inspectionterminal, the fifth inspection terminal, the sixth inspection terminal,and the seventh inspection terminal are used for measuring a resistancevalue of a third object to be inspected.
 9. The circuit board accordingto claim 1, wherein the side surface of the circuit board has one of arecessed portion and a projecting portion formed therein so as toposition a measurement jig when the measurement jig is brought intoabutment against the three or more inspection terminals.
 10. The circuitboard according to claim 1, further comprising a connection wiringconfigured to electrically connect the connection terminal andcorresponding one of the three or more inspection terminals to eachother, wherein the connection wiring is formed on a back surface or inthe inner layer of the circuit board.
 11. The circuit board according toclaim 10, wherein the connection wiring is electrically connected to theconnection terminal and corresponding one of the three or moreinspection terminals via a through hole formed through the circuitboard.
 12. The circuit board according to claim 1, wherein at least oneof the three or more inspection terminals is electrically connected to aground.
 13. The circuit board according to claim 1, wherein at least oneof the three or more inspection terminals is electrically connected to aheat radiation pad configured to radiate heat of an IC included in thecircuit board.
 14. A display device, comprising the circuit board ofclaim
 1. 15. The display device according to claim 14, furthercomprising: a display panel; a frame, which is made of a metal, and isconfigured to support the display panel from a back surface sidethereof; and a protection tape configured to cover the circuit board,wherein the circuit board is arranged on a back surface side of theframe, wherein the protection tape is electrically connected to at leastone of the three or more inspection terminals, and wherein theprotection tape is electrically connected to the frame.